Antenna system



April 1, 1953 A. c. HAYES 2,636,122

ANTENNA SYSTEM Filed April 28, 1949 v nmmm M jw w 62 azg ga PatentedApr. 21, 1953 UNITED STATES PATENT OFFICE ANTENNA SYSTEM Austin 0.Hayes, Melcher, Iowa Application April 28, 1949, Serial No. 90,083

7 Claims. (Cl. 250-33) The invention relates generally to antennasystems and, more particularly, to such a system adapted for eithertransmitting or receiving of relatively high frequency.

The invention has among its objects the production of :a very compact,highly efficient antenna system in which the antenna element or radiatormay be considerably less than a quarter wave length of the operatingfrequency, whereby the same may be used in locations and underconditions which preclude the use of longer antennas.

Another object of the invention is the production of such an antennasystem for use in a transmitting circuit which is capable of radiatingan extremely strong and effective signal.

A further object of'the invention is the production of an antenna systemwhich is capable of effectively receiving radio frequency signals with areduction in undesired interference, particularly man-made electricalinterference, whereby a high signal to noise ratio is achieved.

Many other objects and advantages of the construction herein shown anddescribed will be apparent to those skilled in the art from thedisclosure herein given.

The present invention is directed to an antenna construction which isparticularly efficient as a transmitting antenna, in which case highvoltages may be produced on the radiating element, and very efficienttransmission achieved, employing a radiator of very small length. Forexample, in actual tests an antenna constructed in accordance with thepresent invention, utilizing a radiator length of from seven totwentytwo inches on a mobile transmitter operating at a frequency ofapproximately twenty-seven megacycles, and approximately nine wattsinput produced a signal which was well received in all U. S. districts,the mobile unit being in motion during the tests. Likewise, the antennaby actual test would appear to be almost as efficient when employedunder ground as above ground.

In the drawings, wherein like reference characters represent like orcorresponding parts:

Fig. 1 is an elevational view of an antenna structure embodying thepresent invention, with one side of the housing removed to disclose thedetails of construction;

Fig. 2 is a diagrammatic figure of the circuit embodied in the structureillustrated in Fig. 1;

Fig. 3 is an elevational view, in section, of the application of thepresent invention to a single antenna element; and

Fig. 4 is a diagrammatic figure of the circuit of the antennaillustrated in Fig. 3.

It is well known that the resonant frequency of an antenna may beincreased by adding inductance in the antenna circuit, and may bedecreased by adding capacity. However, in the past it has beenconsidered inadvisable to load an antenna with inductance to radiate awave more than four times the natural Wave length of the antenna, as theinsertion of greater amounts of inductance would normally increase thereactance and reduce the current fiow. The present invention, however,is capable of radiating a strong wave of a length considerably in excessof four times the natural wave length of the radiator. i

Referring to the drawings, and particularly to Figs. 1 and 2, lindicates generally a housing constructed of suitable metal, as forexample, aluminum, having a pair of insulators 2 and 2' mounted thereonwhich respectively carry an antenna element or member 3 and 3', only aportion of the latter being illustrated in Fig. l. Positioned in thehousing I is a pair of inductances 4 and 4' which may be woundonsuitable forms 5, one end of the inductance 4 being connected to theradiator 3, as indicated at B, and one end of the inductance 4'connected to the radiator 3, as indicated at 6'. Also positioned in thehousing I is a small variable condenser, indicated generally by thenumeral 1, having rotor plates 8 operatively connected to the free endof the inductance 4, as indicated at 9, with the stator plates ll of thecondenser being operatively connected to the free end of the inductance4', as indicated at H. Both the stator and rotor plates of the condenser1 are suitably insulated from the housing I, and the effective capacityof the condenser may be varied by rotating the rotor shaft l3 by meansof a suitable knob H, or the like. Inductively radiated to therespective inductances 4 and 4' is a pair of inductances l5 and [5, thelatter being connected in series, as indicated at [6, with theinductances I5 and [5' in the construction illustrated encircling therespective ends of the inductances 4 and 4. The free end I! of theinductance I5 is operatively connected to a suitable terminal l8, andthe free end I!) of the inductance I5 is connected to one end of an aircore choke 2|, the inductance of which is such that it is resonant atapproximately the resonant frequency of the antenna. The opposite end ofthe choke 2| in the construction illustrated is connected to the housingI, as indicated at 22.

Assuming the antenna is adapted to be connected into a transmittercircuit, a coupling loop 23, adapted to be operatively related to theoutput circuit of the transmitter, may be employed, one end 24 of theloop being connected to the terminal H] by a suitably shieldedtransmission line 25, the outer shield of which is grounded, asindicated at 25 in the transmitter circuit, with the other end 21 of theloop 23 being also connected to the shield, the latter, in turn, isgrounded to the housing I of the antenna, as indicated at 28. Thus thehigh voltage side of the coupling loop 23 is operatively connected tothe end H of the inductance [5, while the return path from theinductance I5 is through the choke 2|.

It will be noted that, in the construction above described, the loadinginductances 4 and 4 and condenser 7 form a series resonant circuit.Consequently, as the inductive and capacitive reactances are equal andopposite in polarity at the resonant frequency, they balance each other,and the actual total reactance is reduced to zero. It will, therefore,be apparent that a large current flow may be produced at resonance asthe impedance is a minimum, the only opposition to the current flowbeing that of the resistance in the circuit. Likewise, since a largecurrent flow isobtained at resonance, the actual voltages across theinductance and capacitor may be many times the voltage applied to thecircuit. Also, for frequencies below resonance, the circuit acts likecapacitor plus a resistor, and for frequencies above resonance, thecircuit acts like an inductor plus a resistor, so that a high impedanceis offered to the flow of current other than at theresonant frequency,while a low impedance is presented at the resonant frequency.

It will also be apparent that as the return path from the inductances l5and i5 isthrough the choke, 2|, which is substantially resonant at thetransmitting frequency, the return flow of current at the transmittingfrequency is opposed by the choke and, in effect, forces the radiofrequency alternations through the resonant antenna circuit to build upthe high radio frequency voltage therein. In actual tests, antennas ofthis type, employing relatively very short radiators, are capable oftransmitting a very strong wave.

The present invention is equally applicable to a singlepole antenna, andsuch a construction is illustrated in Figs. 3 and 4, of the drawings,whereinthe reference numeral 41 indicates generally a metallic housinghaving, in the present instance, a cylindrical tubular portion 52extending therefrom, an insulator 43 being mounted on the outer end M ofthe portion 32. Positioned in the portion d2 of the housing is aninductance 45 which may be wound upon a suitable form 48, the upper end41 of the inductance being operatively connected to a single antennaelement or radiator 48 by means of the connecting member 49, theopposite end 5| of the inductance 45 being connected to the statorplates 53 of a variable condenser 52, the rotor plate 54 thereof beinggrounded to the housing 4! through the condenser frame 55, which is notinsulated from the housing. The efiective capacity of the condenser 52may be varied by rotating the shaft 56 of the condenser by means of asuitable knob 51, or the like, whereby the circuit may be tuned toresonance at the desired frequency. Inductively related to theinductance and, in the present instance, illustrated as being positionedwithin the latter is a second inductance 58,

the latter being suitably supported by a member 59 of suitableinsulating material extending across the lower portion of the housing 4|and rigidly secured thereto by brackets BI, or other suitable means. Theend 62 of the inductance 58 is operatively connected to a suitableterminal 63 by a conductor 64, while the other end 65 of the inductanceis connected to ground through an air core choke E6, the free end of thelatter being connected to. the housing 4!, as indicated at 51.

Assuming the antenna is to be used as a transmitting antenna which maybe coupled to the transmitter by means of the transmission line 25 andcoupling loop 23, heretofor described, whereby the side 25 of the loop23 is connected to the inductance 58, and the other side 27 of the loopgrounded to the housing ii. It will be noted that, as in the twinelement construction, a series resonant antenna circuit is employed and,in like manner, a choke is inserted in the return path of the couplinginductance, so that, in operation, the same advantages are achieved withthe main difference being that the first construction is, in effect, twosingle antenna elements operated out of phase.

The inductances and capacities employed in any particular instance will,of course, depend upon the desired frequency size of the shield housing,etc., and all conductors are insulated by suitable material, asrequired. While the length of the radiators is not critical, I havefound-that excellent results may be obtained on the various frequencieswith radiators of the length specified in the following table:

Frequency in Megacycles Radiator Length,

22" each (2) used. 17%. 36".

66"bach (2) used. 50".

Likewise, the size or shape of the radiator or antenna element may beconsiderably varied, and may be straight, circular, spherical, or bent,or may be in the form of a gaseous tube as may be desired for a,particular application. Similarly,

ter or receiver, in which case the housing may form a part of thehousingor cabinet of such transmitter or receiver.

The directional characteristics ofgthe antenna may be varied by the use,of director or reflector elements. and the antenna construction illus--trated in Figs. 1 and 2 would appear to have marked directionalcharacteristics. For example, if the radiators 3 and 3' are bent, asindicated in dotted lines in Fig. 2, av very directional signal may beobtained in the direction of the dotted arrows in Fig. 2, in which case.the radiators 3 and 3 would be bent at an angle of. approximately fiftydegrees.

fhe system is also very effective for receiving signals, as Well as thetransmission thereof, and

would appear to have a very marked action in the.

reduction of interference, particularly local electrical interference,and the like, with anincrease in the signal strength at the particularfrequency at'which the antenna is resonant achieving a very high signalto noise ratio.

1 While the above description of the present invention, and the methodof operation set forth may, in part, account for the high efficiency of'such antenna, the phenomena responsible for the exceptional resultsobtained is not fully understood at the present time. It may be possiblethat the transmission of radio waves with the present antenna involvesconcepts heretofor not considered in connection with previous type oftransmission of radio waves, whereby possibly a closer matching ofatmospheric resistance, or the like, is achieved with the wavespropagated possibly being of greater similarity to the natural wavesalways present between the earths field and outer space.

7 Having thus described my invention, it is obvious that variousimmaterial modifications may be made in the same without departing fromthe spirit of my invention; hence, I do not wish to be understood aslimiting myself to the exact form, construction, arrangement, andcombination of parts herein shown and described or uses mentioned.

What I claim as new and desire to secure by Letters Patent is:

1. In an antenna system, the combination of a pair of electricallyconductive antenna members operating out of phase, a ground therefor, apair of inductances, each arranged in series with a respective antennamember, a variable capacitor operatively positioned between saidinductances and connecting said inductances in series and operative totune the circuit so formed to the desired operating frequency forming a,series resonant circuit, a second pair of inductances each closelycoupled inductively to a respective first mentioned inductance whereby ahigh voltage is produced on each of the antenna members, said secondpair of inductances being connected in series and adapted to beoperatively connected to a radio signal device, and a choke operativelyconnected through said shielded transmission line in series with one ofsaid second inductances and said signal device, said choke beingresonant to approximately the desired operating frequency, wherebyeffective transmission of radio frequency signals is obtained.

2. In an antenna system, the combination of a pair of electricallyconductive radiating elements operating out of phase, each having aphysical length substantially less than a quarter wave length of thedesired operating frequency, a ground therefor, a pair of inductances,each arranged in series with a respective radiating element, a variablecapacitor operatively positioned between said inductances and connectingsaid inductances in series forming a. series resonant circuit andoperative to tune the circuit so formed to the desired operatingfrequency, a second pair of inductances each closely coupled to arespective first mentioned inductance whereby a high voltage is producedon the radiating elements, a shielded transmission line operativelyconnected to the ground, said second pair of inductances being connectedin series and adapted to be operatively connected through said shieldedtransmission line to a radio signal device, and a choke operativelyconnected in series with one of said second inductances and such signaldevice, said choke being resonant to approximately the desired operatingfrequency, whereby efficient 6 transmission is obtained employingradiating elements substantially less than a quarter wave length.

3. In an antenna, system, the combination of an electrically conductiveantenna member, a ground therefor, an inductance and a variablecapacitor arranged in series with said antenna member and operativelyconnected to ground, operative to tune the circuit so formed to thedesired operating frequency, a shielded transmission line, a secondinductance inductively coupled to the first mentioned inductance,whereby a high voltage is produced on the antenna member, and adapted tobe operatively connected to a radio signal device through said shieldedtransmission line, and a choke operatively connected in series with saidsecond inductance and to ground, said choke being resonant toapproximately the desired operating frequency, whereby efficienttransmission is obtained.

4. In an antenna system, the combination of an electrically conductiveantenna member, having a physical length substantially less than aquarter wave length of the desired operating frequency, an inductanceand a variable capacitor arranged in series with said antenna member,operative to tune the circuit so formed to the desired operatingfrequency, a second inductance inductively coupled to the firstmentioned inductance, whereby a high voltage is produced on the antennamember, and adapted to be operatively connected to a radio signaldevice, and a choke operatively connected in series with said secondinductance, said choke being resonant to approximately the desiredoperating frequency, whereby efiicient transmission is obtainedemploying an antenna member substantially less than a quarter wavelength.

5. An antenna structure comprising, in combination, a laterally spacedpair of electrically conductive antenna members, insulators for mountingth antenna members, a housing for mounting the insulators, a pair ofinductances mounted within the housing, each inductance connected to itscontiguous antenna member, a variable condenser mounted within thehousing and connected in series between the inductances, and operativeto tune the circuit so formed to the desired operating frequency forminga series resonant circuit, a second pair of inductances mounted withinthe housing and about the first pair of inductances, and closely coupledinductively to a respective first-mentioned inductance, said second pairof inductances being connected in series and adapted to be operativelyconnected to a radio signal device, and a choke positioned within thehousing and operatively connected in series with one of said secondinductances and said signal device, said choke being resonant toapproximately the desired operating frequency.

6. A directional antenna structure comprising, in combination, alaterally spaced pair of angularly bent, electrically conductivemembers, each member comprising a, straight portion and a bight portionformed at an angle thereto, insulators for mounting the antenna members,a housing for mounting the insulators, a pair of inductances mountedwithin the housing, each inductance connected to its contiguous antennamember, a variable condenser mounted within the housing and connected inseries between the inductances, and operative to tune the circuit soformed to the desired operating frequency forming a series resonantcircuit, a second pair of inductances mounted within the housing andabout the first pair of inductances, and closely coupled inductively toa respective first-mentioned inductance, said second pair of inductancesbeing connected in series and adapted to be operatively connected to aradio signal device, and a choke positioned within the housing andoperatively connected in series with one of said second inductances andsaid signal device, said choke being resonant to approximately thedesired operating frequency, whereby a directive antenna structure isobtained having a straight portion and bight portions formed at an angleto the straight portion and lying in the same plane.

7. An antenna structure comprising, in combination, an electricallyconductive antenna member, an insulator for mounting the antenna member,a housing having an elongated portion for mounting the insulator, aninductance mounted within the elongated portion of the housing andconnected in series with the antenna member, a variable condensermounted within the housing and connected in series with the inductance,operative to tune the circuit so formed References Cited in the file ofthis patent UNITED STATES PATENTS Name Date Bethenod Sept. 9, 1924Batsel Feb. 17, 1925 Schafier Nov. 5, 1930- Van Arco Jan. 5, 1932.Newman Apr. 12, 1938 Landon Nov. 1, 1938 Crossley Nov. 19,1940Roosenstein May 13, 1941. Lake et a1. July 15, 1947 Number

